[linux-lvm] Powerfailure and snapshot consistency
Mike Snitzer
snitzer at redhat.com
Mon Mar 28 18:34:39 UTC 2011
On Mon, Mar 28 2011 at 1:24pm -0400,
Stuart D. Gathman <stuart at bmsi.com> wrote:
> On Mon, 28 Mar 2011, Phillip Susi wrote:
>
> >On 3/27/2011 5:55 PM, Stuart D. Gathman wrote:
> >>Don't need help, just trying to understand the event. So from what you
> >>said, the problem probably stems from the RAID1 resync, which could
> >>make one PV "older" than the other.
> >
> >The data is written to the primary mirror first, so this can't happen.
> >Proper use of barriers will prevent this whole scenario, so my guess is
> >that you are using ext3 ( which defaults to nobarrier ) or explicitly
> >mounting ext4 with nobarrier.
>
> Ah, thank you! Yes, I am using ext3 with EL5.5 defaults, and will now learn
> about the barrier option. Seems like a good thing to turn on when "replace
> battery" comes up on the ups.
RHEL5.x's DM doesn't support barriers (nor does MD afaik).
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